Sound recording apparatus



March 4, 1941. ZIMMERMAN 2,233,907

SOUND RECORDING APPARATUS Filed Dec. 29, 1958 2 Sheets-Sheet 1 8g I I Zhwentor March ,1941. A. G. ZIMMERMAN 3 7- SOUND RECORDING APPARATUS Filed Dec. 29, 1958 2 Sheets-Sheet 2 LEI attorney ZSnnentor Patented Mar. 4, 1941 v 2,233,907

UNITED STATES PATENT OFFICE 2,233,907 SOUND RECORDING APPARATUS Arthur G. Zimmerman, Indianapolis,-lnd., assignor to Radio Corporation of America, a corporation of Delaware Application December 29, 1938, Serial No. 248,250. 1 Claim, (01. 88-23) This invention relates to sound recording aping optical system with my photometric attachparatus, and more particularly to apparatus for ment applied thereto and with the cover rephotographically recording sound on film. The moved, and particular feature involved is a novel attach-. Figure 2 is a side view taken from the bottom 5 ment for commercial sound recording systems of Fig. 1 and showing the same type of optical which will indicate at any time the effective system with a portion of the casing broken away. brightness of the recording light. The recording optical system shown in the In the recording systems heretofore used which drawings is of the commercial type generally included either a galvanometer or light valve for known as the RCA Photophone recording sysmodulating the light beam, it has been customary tem, and the optical elements thereof, as well as to use a high intensity incandescentlamp as the the operation of the system in producing varilight source. These incandescent lamps have a ous types of sound track, are described in denormal life of the order of fifty hours, and the tail in an article appearing on pages 258 to 2'73 brightness thereof changes during their life. In of the Journal of the Society of Motion Picture order to maintain the light constant during the Engineers for Sep 1937- se deta s recording of a given section of film, it has been are, in general, immate i to h p s nt incustomary to provide an ammeter in series with vention and only such of them as e c y the lamp and to maintain the current through pertinent are specifically referred o e na ter. the lamp at a constant value. This has not been In e p c y te an e p nd sufficient to maintain the lamp at perfectly unicalled at II is p ed in a light-tight a i 20 'form brightness, as the tungsten which evapht f m t is t r a p p s u h orates from the lamp filament is deposited on 0118 hOuSing which y e e lenses, the glass envelope and some times absorbs a p s, ground noise reduction shutters, etc..

very considerable portion of the light. The to the condenser lens 13, which directs the light amount of filament material deposited in a given to the mirror of the galvanometer 14. Light is location on the lamp envelope varies from lamp reflectedby the galvanometer to a second housto lamp and is not predictable, so that, with a ing or tube indicated at I5 which carries a nargiven change in the electrical characteristics of row slit adjacent the end thereof generally indithe fil Corresponding change in the cated at it and at the other end carries an ob- 30 brightness of the lamp did not always follow. jective II which serves to focus the recording In the apparatus of the present invention, an light upon the film 28 at the recording point. appropriate photometer is attached to and in- Within the beam of light, but below the portion terconnscted with the mechanism of the optical thereof which passes the slit, there is provided a system so that at any time during intervals bemirror l8 which directs a portion of the light to 5 0 tween actual sound records the brightness of the an appropriate monitoring. apparatus such, for lamp emitted by the lamp may be conveniently example, as that described and claimed in and p y measured. Sachtleben Patent No. 2,206,645, issued July 2,

One object of thc-invention is to provide an 1940- 10 improved photometer for measuring the bright- A secondmirror I9 is provided which is mov- 40 ness of incandescent lamps. able in a plane closely adjacent the slit of the Another object of the invention is to provide recording system. This mirror I9 is mounted an improved photometric attachment for photoupon a shaft 20- which is rotatable in an approphonographic recorders. priate bearing formed in the casing 24 of the Another obJect of the invention is to .provide apparatus. The mirror l9 may either be a glass 5 a photometric device which may be attached to mirror or it may be an appropriate plated metal standard commercial recording optical systems surface, in either case being attached by the arm and which will permit substantially instantane- -2l to the shaft 20. This arm 2|, as shown in both ous readingsof the recording lamp brightness. figures of the drawings. has an enlarged cylindri- Other and incidental objects of my invention cal portion which fits over the shaft 20 and which 50 will be apparatus to those skilled in the art from carries on its external surface the spring 22, a reading of the following specification and an which rotates the mirror downwardly out of the inspection of the accompanying drawings in light beam.

which At the opposite end of the shaft 20 there is at- Figure 1 is a top view of a commercial recordtached a handle 23 for rotating the shaft 20 and type which generates a current, depending upon the amount of light incident thereon. The current produced by the cell 25 is carried to the meter 26 by the leads 21. The meter 26 may, as shown in the drawings, be mounted on the side of the case 24 or it may be mounted in any other convenient location.

It will be apparent that when thehandle 23 is depressed to bring the mirror is into operative position the current through the exclter lamp l I may be adjusted to give a predetermined reading on the meter 26, and the exposure of the sound record film may thereby be maintained constant. This operation can be performed quite rapidly and may even be accomplished during the momentary pause between the speech of different actors or in similar short pauses during the recording operation.

Having now described my invention, I claim: In combination, a sound recording optical system having a light source and means for direct-.

ing light from said source in a beam along a predetermined path, photoelectric means adjacent said path, light-intensity indicating means connected to said photoelectric means, light reflecting means, and rotary means movable about an axis parallel to said path for moving said light reflecting means into the path of the said light beam for reflecting the light of said beam to said photoelectric means.

ARTHUR G. Z IMMERMAN. 

